Get full access to Outside Learn, our online education hub featuring in-depth nutrition, fitness and adventure courses, and more than 2,000 instructional videos when you sign up for Outside+..
Since our bodies naturally make vitamin D when we’re exposed to the sun, it might seem as though we don’t need to worry about getting enough during the summer months-but beware. For one thing, sunscreen blocks the process, and a tan, or naturally darker skin, reduces vitamin D synthesis. A study of nearly 1,000 sun-loving Brazilians who live close to the equator found that most had vitamin D levels below optimum.
Vitamin D has far-reaching benefits, including stronger bones, a healthier heart, better immune function, and healthier lungs. Among toddlers, healthy levels of the vitamin correlate with more muscle mass and less body fat. Lack of vitamin D has been linked to higher risk of:
- Heart attack
- Heart failure
- High blood pressure
- Alzheimer’s disease
- Multiple sclerosis
- Crohn’s disease
- Other autoimmune diseases
How Much Do You Need?
The best way to identify individual needs is with a blood test, available through medical and naturopathic physicians. Optimum levels range between 30 and 60 ng/mL. Below 20 ng/mL is considered deficient and up to 100 ng/mL is considered safe. Otherwise, nutritionally oriented health professionals often recommend taking 1,000-2,000 IU daily to maintain optimum levels.
Can You Take Too Much?
When Mayo Clinic researchers examined more than 20,000 vitamin D test results for safety, they found only one case of toxicity-and that was in a patient who had taken extremely high doses: 50,000 IU daily for more than three months. The Institute of Medicine, at the National Academy of Sciences, recommends an upper limit of 4,000 IU per day.
Did You Know?
Menstrual cramps can be a sign of vitamin D deficiency.